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Is Nulling Alone Enough? NO!! Alice Bob Chris Transmit Nothing!!! NO! null Do we really need to null at all antennas? No, we can use interference alignment Do we really need to null at all antennas? No, we can use interference alignment

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Interference Alignment If I 1 and I 2 are aligned,  appear as one interferer  2-antenna receiver can decode the wanted signal N-antenna node can only decode N signals 2-antenna receiver I 1 + I 2 wanted signal

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aligning Use Nulling and Alignment Alice Bob Chris nulling Alice + Chris (unwanted) Bob Can decode Bob’s Signal and (Alice + Chris) All senders transmit, but the throughput is as high as if only the 3-antenna node is transmitting all the time

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General Protocol Each sender in a distributed way computes  where and how to null  where and how to align Analytically proved:  # concurrent streams = # max antenna per sender